Frenz a écrit: • A Boeing source dated August 2008 advertised a revised airframe supporting this weight increase. This includes strengthening of the outboard wing, the center wing box, the wing leading edges, the MLG (Main Landing Gear) wheels well, and the center fuselage as well as enhancing manoeuvre load alleviation.

By : Dominic GATES : Seattle Times aerospace reporter[quote] The Federal Aviation Administration (FAA) has quietly decided to loosen stringent fuel-tank safety regulations written after the 1996 fuel-tank explosion that destroyed flight TWA 800 off the coast of New York state.[/quote]

The FAA proposes to relax the safeguards for preventing sparks inside the fuel tank during a lightning strike, standards the agency now calls "impractical" and Boeing says its soon-to-fly 787 Dreamliner cannot meet.

In a lightning storm, the critique said, the less stringent rules could leave a commercial airliner "one failure away from catastrophe."

Les paroles sont fortes !

FAA management, contradicting its own technical staff, argues that relaxing the spark-prevention standard is balanced by new technology to reduce fuel-tank flammability that will increase safety overall.And Boeing experts insist the 787 will be safer in a lightning storm than any jet flying today.

"It appears that management has overruled the judgment of the people that have day-to-day responsibility for the safety of aircraft," Hall said.

Cela sent le lobby !

The TWA 800 rule

The average commercial airplane is hit by lightning about twice a year, Boeing estimates. A dangerous electrical spark may occur if current passing through an airframe reaches a small gap between metal parts and jumps across the gap.

Yet because of well-developed protection systems, it's been more than 45 years since a U.S. airliner was brought down by lightning.

Cela est vrai !

The rules the FAA is now reinterpreting have been in place since 2001 after the investigation into the TWA 800 fuel-tank explosion that killed all 230 people on board the 747 jumbo jet.

While investigators concluded that the likely cause of the spark that triggered that explosion was faulty wiring,they set up standards to prevent fuel-tank ignition from any source, including a lightning storm.

Ceci fait partie de l'approche "inerting" !

The rules address two distinct areas: preventing sparks in the tank and reducing the flammability of the vapor inside the tank.

"To this day, we have not had one manufacturer that has been able to demonstrate compliance with that rule," said Ali Bahrami, head of the FAA's Seattle office dealing with commercial-airplane certification.

The FAA granted exemptions in 2006 and 2007 to plane makers Dassault Aviation, of France, and Hawker Beechcraft, of Wichita, Kan., allowing them to certify their Falcon 7X and Hawker 4000 business jets with only two independent layers of protection on the wing-skin fasteners.

Détails significatifs , tout de même !

In a detailed briefing on the 787's protection systems, two high-level Boeing lightning experts — who spoke on condition that they not be named — said the Dreamliner cannot meet the requirement.

"Boeing spent years trying to develop triple layers of structural lightning protection for every 787 fuel-tank fastener and joint, but we were unable to identify the technical means at many locations in the wings," one said.

The concerned FAA engineers detailed where these three vulnerabilities are on the 787:• The aluminum shear ties that attach the wing ribs to the spars could crack.• A wing-skin fastener could break, popping the sealant on the head.• On fasteners inside the fuel tank, a coat of sealant covering a gap between fastener head and sleeve could deteriorate.

Indeed, Boeing lightning lab tests in 2007 revealed an unexpected amount of sparking inside the 787's wing tank as then designed, caused by gaps between fastener heads and sleeves.

Il a dû y avoir une réponse de Boeing !

In response, Boeing's engineers turned around thousands of fasteners, putting the heads on the outside instead of inside the fuel tank. Following this redesign, engineers weighed the worst-case lightning threat at every location and demonstrated that there was sufficient margin to rule out sparking.

For those fasteners that couldn't be turned around, a brush coat of sealant was added as an extra precaution, the Boeing experts said.

Idem !

"The issue is totally resolved now," one of the experts said.Likewise, the Boeing engineers said, shear-tie cracks and broken fasteners have proven not susceptible to sparking under the worst-case level of lightning current.

Il va y avoir des tests, tout de même !

"The level of detailed design, test, and analysis (in the 787's wing-tank lightning protection) ... is greater than has been conducted previously in aviation," one said.

Reducing vaporThe FAA claims the less stringent anti-sparking rule is balanced by an important new safety feature of the 787: its fuel-tank inerting system.

OK ! Bonne nouvelle ! A voir & à suivre !

As the level of fuel inside the wing falls during flight, the system pumps inert (nonflammable) nitrogen gas into the space created. That hugely reduces the danger of flammable vapor.When the original 2001 rule was written, the FAA stated that it would consider relaxing the ignition-source rules in the future if there was improvement in the technology to lower flammability — "such as full-time fuel-tank inerting."

OK. Vu !

By all accounts, the 787's inerting system is very effective. But there's a catch: The FAA is not requiring that it be "full time."

Voilà une faille !

If a 787's inerting system breaks down, to save the expense of grounding the plane, an airline will be free to continue to operate it for 10 days while waiting for replacement parts.

During those 10 days, the possibility — however remote — of potential failures in the three areas with single anti-spark features looms as unacceptably dangerous to the FAA engineers represented by NATCA.

C'est bein compris ! Voir notre remarque immédiatement ptécédente !

"This inerting system, if it was full time, it would definitely be an acceptable level of safety," said a second FAA engineer who has worked on the 787's certification.

L'utilité de ce degré de prudence est claire !

But without that assurance, he said, to fly on a Dreamliner out of a lightning-prone airport in the summer is a risk he's not prepared to take.

A noter !

"I wouldn't put my family on a 787 out of Miami," said the engineer, who formerly worked for Boeing.

Il le dit comme il le pense !

In contrast, Boeing's 787 lightning-team leader sees the inerting system as a bonus safety feature rather than an essential requirement. He is willing to rely on Boeing's exhaustive testing of every potential spark point in the wing.

"I wouldn't hesitate to get on the plane," he said. "I know more about the structural protection on this airplane than I do on anything else we've ever built."

Espérons -le !Et qu'il a raison !

FAA, Boeing too close?Tomaso DiPaolo, NATCA's aircraft-certification national representative, charges that when FAA engineers raised their safety concerns internally management simply removed them from the team developing the new policy.

Cela n'est pas rassurant !

The FAA ignored its own technical people, he said, while making sure Boeing agreed with the policy change."It's another example of the FAA getting too close to industry," said DiPaolo.

A Boeing internal document reviewed by The Seattle Times shows the company had a "team to assist FAA in wording of interpretation" of the lightning rule for the 787 as far back as August 2004, just eight months after the new jet program launched.The FAA's Bahrami insisted that the policy change has been crafted to work for all airplane manufacturers with no special treatment of Boeing. "Boeing is only one customer," Bahrami said.

The Boeing Co., whose delayed 787 Dreamliner has been further postponed by the Machinists' strike, said ...that a critical problem concerning brake software has been resolved, putting the plane one step closer to first flight."The issues with the brake software are largely behind us," said Yvonne Leach, a Boeing spokeswoman in Everett, where the plane is being assembled. "Functionality required for flight test is in the labs and is working well."The 787 Dreamliner......uses new electric brakes rather than hydraulic as on most planes. Pat Shanahan, the program manager, said in May that the brakes and power system were the last two problem areas as Boeing prepares for first flight and aims for a first delivery in the third quarter of 2009.......Shanahan said in July that subcontractor Crane Co. hadn't been able to get software it was developing for the brakes certified for use. Leach said ....that "all known software problems are resolved" and that the brakes are now being tested.......the problem had been "due to a traceability anomaly" in "highly advanced software being rewritten for the brakes."

Boeing is to incorporate a redesign to the landing gear on later production 787-8s to speed gate turnaround operations by improving the thermal performance of part of the braking system.

As Boeing announces it has cleared all 787 equipment for first flight, it has emerged that early 787s will be constrained in some quick turnaround operations if the gate arrival follows a high-energy landing that raises the brake temperature past a certain threshold. Boeing emphasises that the issue lies not with the brakes themselves, but the remote data concentrator (RDC) units on the four 787 main landing gear axles.RDCs are used to flow digital and analogue data from remote sensors into the 787's Common Core System and replace traditional, dedicated signal wiring, saving weight and allowing increased operator flexibility.

Brake cooling time would vary based on airport conditions and a specific duration of time would not be specified, though brake temperature would have to return to acceptable levels before pushback.

Voir remarques ci-dessus !

A high-energy landing would, for example, be undertaken if a higher autobrake setting were selected to reduce stopping distance on a shorter runway.

Exact (évidemment).

To improve turnaround time following high-energy landings that would significantly raise brake temperature, Boeing along with partner GE Aviation, who supplies the RDCs, is developing a more robust installation that will relocate the unit and improve thermal performance.

GE est le fournisseur de ces machins (RDC) !

The design change will maintain the functionality of the landing gear RDCs, but Boeing will have to revise the brake control monitoring system software to maintain compatibility with the new component package.

Boeing expects production incorporation to tentatively occur in late 2010, which when matched up against the airframer's proposed production ramp-up, could be part of the blockpoint changes expected for aircraft number 20.

Pas étonnant que les clients veuillent éviter ces 20 premiers !

Boeing adds that the fix will be implemented as soon as it is available and the company is still working out the exact timing of the change.

D'où les discussions serrées et compliquées avec tous les clients !

Meanwhile, Boeing says "all equipment for first flight has been cleared" as it prepares for the twinjet's maiden sortie in the second quarter.

He cites several visible "mini-milestones" expected in the coming weeks, including a trip to the paintshop and the start of gauntlet tests to verify and validate systems integration, as well as flight line ground and ship power testing to ensure the aircraft's self-sufficiency.

Boeing today launched the first of three phases of gauntlet testing on the first 787 flight test aircraft, ZA001, as the programme edges closer to first flight.The factory gauntlet is the first phase of full integrated systems testing that sees ZA001 hooked up to an external computer and "flown" in a simulated environment to see how systems react.

Gauntlet testing also marks the handover of the first 787 from the assembly workforce to the flight test team.

C'est le "Flight Test Team" qui donne les coups !

Most of the aircraft's onboard systems will be tested during the first phase of the gauntlet. The aircraft's power will be drawn from ground cart and battery. The engines and auxiliary power unit (APU) will not be turned on during this indoor phase of gauntlet testing.

Ils n'y vont pas trop fort tout de même !

The final two phases of gauntlet testing, intermediate and final, will both take place once ZA001 exits Building 40-24 for the Everett flight line.

Boeing has accelerated the pace of the 787programme as it targets a first flight by the end of June. Keymilestones required for the maiden sortie have been completed, butquestions remain about the production ramp-up effort.

The airframer completed the factory gauntlet on 20 April, the firstof three closed-loop simulations tests, marking the hand-off of 787prototype "ZA001" to the flight-test team. Programme sources indicatethat the factory "gauntlet test" was accomplished faster thananticipated.In addition, the static-test airframe also conducted its third andfinal pre-first-flight requirement on 21 April, with the wings beingflexed to limit load, ie 100% of the load expected to be seen inservice. Boeing emphasises that analysis of the test, which saw thewings pushed 20-30% beyond limit load towards ultimate load, isongoing, but appears positive.

Structural components for the first production aircraft - theseventh airframe that had been designated ZA007 but is now dubbed ZA100- have begun arriving at the assembly line in Everett, Washington, andinclude the wings and aft fuselage. The designation for firstproduction 787 was changed after Japanese airlines assumed control ofmany early delivery slots from Chinese carriers.Other tests ahead for ZA001 in the near term include finallanding-gear swing tests before it is moved to the flight line for theintermediate gauntlet trial, which will see the 787 fuelled for thefirst runs of the Hamilton Sundstrand APS 5000 auxiliary power unit andRolls-Royce Trent 1000 engines.Boeing says all hardware and software is ready to support a firstflight later in the second quarter as currently scheduled, althoughsome industry analysts are sceptical, suggesting that the event couldslip in July.Boeing chief executive Jim McNerney expressed confidence in theprogramme schedule during the company's quarterly earnings call on 22April, as it progresses toward flight testing, roughly 22 months laterthan originally planned. However, the airframer is still being pressed about its productionramp-up plan and whether or not its fragile supply chain can perform tothe level of demand. Ron Epstein, analyst for Bank of America/MerrillLynch recently questioned the plan, citing build times of over 300 daysfor centre fuselage sections by Global Aeronautica.McNerney reaffirmed that Boeing's 50% purchase of the NorthCharleston, South Carolina facility has added "significant" productionstability and the integrator is no longer a "bottleneck" for theprogramme. However, McNerney cautioned that Boeing is a year away fromevaluating 787 production rates following the initial deliveries as itgauges global demand for the new long-range twinjet in the wake of thecurrent economic turmoil, leaving the door open for a futurereadjustment.

Good news and maybe not-so-good news for Boeing’s 787 flight test preparations this weekend. Sources in Everett suggest that while landing gear retraction tests went better, and faster, than expected in at least two configurations, the test team has hit unexpected electrical system problems on ZA001. On Saturday Boeing decided it would have a special test to trouble-shoot the issue on Sunday afternoon, but by the morning of Apr 26th it was decided to indefinitely delay the electrical system test. No word as yet on what exactly the issue was, or whether it will delay the start of intermediate gauntlet tests – the next big milestone on the road to first flight. Stay tuned.

Boeing is providing new details about what the 787 and its sister ships will do as part of its upcoming flight test and certification plan, noting that nearly 60% of the documentationrequired for certification has been submitted to the FAA.

Once it begins the flight test effort, ZA001 will be used to explore the fundamental aerodynamics and handling qualities envelope. This includes flutter, stability and control,flight controls, major systems work, low-speed handling including stalls, and checks of the full data system.

The flight test fleet is made up of six aircraft, four (ZA001-004) of which are Rolls-Royce Trent 1000-powered and two (ZA005-006) of which are General Electric GEnx-1B powered.

The second aircraft (ZA002) will test stability and control, autopilot, avionics, propulsion and electric systems.

ZA005 will also repeat some flutter work because it is the first GEnx-1B powered version, as well as performing stability and control, aerodynamic performance, propulsion, avionics,community noise and ETOPS. The second GE-powered aircraft, ZA006, will undertake lightning-specific EME tests, and HIRF, more ETOPS and miscellaneous tests with minimal analog requirements.

Mike Delaney, vice president and chief project engineer on 787, says nearly 60% of thedocumentation required for certification has been submitted and, of the remaining 40%, less than 10% will be generated as part of flight tests. "There are about 4,000 deliverables we will deliver to the FAA. Of the remaining parts, around 300 are flight test dependent," he adds.

The 787 is currently subject to 152 issue papers with the FAA covering minor details of thecertification requirements. "Boeing and the FAA are in negotiation on those," says Delaney. The aircraft is also subject to 16 special conditions - many of which cover the new technology areas such as the composite primary structure that have not previously been certificated.